Roads and the like



June 2, 1964 v F. FOULGER ROADS AND THE LIKE Filed Jan. 16, 1961 UnitedStates Patent M 3,135,176 ROADS AND THE LIKE Frank Foulger, GerrardsCross, England, assignor to British Cellophane Limited, Bridgwater,Somerset,

England, a British company Filed Jan. 16, 1961, Ser. No. 82,906 Clalmspriority, application Great Britain Feb. 3, 1960 7 Claims. (Cl. 94-18)This invention is for improvements in or relating to roads and the likeand is concerned with structures of the type comprising a concrete baselayer and an adherent surface layer known as black top or flexiblepavement which comprises a tarry or bituminous material.

Such-roads are usually constructed by first laying a concrete base on asuitable foundation and after curing of the concrete applying a surfacelayer of a bituminous macadam or asphalt which is generally laid at anelevated temperature of about 193 to 250 C., or stone and the likecoated with tar or cutback bitumen which may be laid at ambienttemperatures. On setting, the surface layer adheres to the concrete baseand forms the wearing surface of the road. If required, the degree ofadhesion of the surface layer to the upper surface of the concrete maybe increased by the application of a suitable adhesive material.

As concrete expands or contracts under the influence of temperature andclimatic changes, it is the practice to provide transverse, andsometimes longitudinal breaks or gaps in the concrete base to allowfreedom of movement without distortion of the base. Such breaks in thebase are known as expansion joints and are usually filled withbituminous material. Further, during the curing and settling of freshlylaid concrete, contraction occurs and undesirable breaks or cracks oftenappear in the surface of the base. These breaks also are usually filledwith a bituminous material.

When a surface layer is applied to a concrete base having such breaks inits surface, the surface layer, in time tends to crack in positionscorresponding to the underlying breaksdue to relative movements of theconcrete masses each side of the breaks.

Such cracks in-the surface layer are most undesirable since they permitseepage of water beneath the surface layer and'rapidly causedeterioration of the road surface and the foundation.

In British patent specification No. 812,215, there is described a methodof surfacing a concrete base or foundation structure for a road or likeconstruction wherein relatively thin metallic sheet material is laidover expansion gaps and/ or cracks in the structure prior to theapplication of a surfacing layer to prevent the surfacing layer fromadhering to the foundation structure in the vicinity of the gaps orcracks.

Although the method of the prior art is effective to some degree inpreventing cracking of the surface layer there is scope for improvementsince the surface layer is inclined to adhere to the metallic sheetmaterial and expansion or contraction of the surface layer immediatelyabove the sheet material is restrained.

An object of the present invention is to provide an improved means forreducing the tendency of the surface layer to crack when applied to aconcrete base having breaks, for example expansion joints, in itssurface.

Accordingly, the present invention includes a road or like structurecomprising a concrete base layer and an adherent surface layer of atarry or bituminous material wherein one or more breaks in the concretebase layer are each covered with a bridging member having at least onthe upper surface thereof in contact with the surface layer, a polymericmaterial which is substantially resistant 3,135,176 Patented June 2,1964 to tarry and bituminous products and has a softening point abovethe temperature at which the surface layer is laid.

A preferred polymeric material for use in the present invention,particularly in respect of surface layers laid at elevated temperaturesis polycaprolactam (known as Nylon 6) which has a softening point atabout 221 C.

Examples of other suitable polymeric materials are the condensationproduct of hexamethylene diamine and adipic acid (known as Nylon 66)which has a softening point at about 277 C., polytetrafluoroethylenesuch as is marketed under the Registered Trademark Teflon and has asoftening point at about 327 C., polychlorotrifiuoroethylene such as ismarketed under the Registered Trademark Hostaflon and has a softeningpoint at about 221 C. and the polymer of 3,3 bis(chloromethyl)oxacyclobutane such as is marketed under the Registered 'gademark Pentonand has a softening point at about Such polymeric materials are found tobe substantially non-adherent to tarry and bituminous materials so thatthe surface layer of the road or the like immediately above the bridgingmember is free to move with respect to the bridging member. It is foundthat this. degree of freedom substantially prevents the cracking of thesurface layer at places corresponding with underlying breaks in theconcrete base layer. Further, the polymeric materials, apart from beingunaffected by the elevated temperatures at which surface layers areusually applied and the aromatic and aliphatic products in the surfacelayers, are able to withstand prevailing climatic conditions for aconsiderable period without deterioration of their properties.

Polyethylene is unsuitable for use in the present invention, even whenthe surface layer is laid at ambient temperatures, since it rapidlydeteriorates in the presence of aromatic and aliphatic hydrocarbonspresent in tarry and bituminous materials.

Where the break in the concrete is relatively small in width, thebridging member may consist of a single sheet of the polymeric materialsalthough it is preferable to support the polymeric sheet with anunderlying sheet of a suitable stiffening material such as a metallicsheet, for exmple of hard tempered aluminium or copper, which may besecured to the polymeric sheet and which is capable of withstanding theelevated temperature to which it may be subjected during the laying ofthe surface layer and capable of withstanding the climatic conditionswithout substantial deterioration. I

In a further form of the invention, the bridging member comprises alength of flattened tubing of the polymeric material which is laid withits longitudinal axis parallel with the break in the concrete baselayer. However, in the preferred form of the invention the bridgingmember comprises a length of flattened tubing of the polymeric materialhaving inserted inside the flattened tubing a sheet of a stiffeningmaterial capable of withstanding the conditions to which the bridgingmember will be subjected. The stiffening material minimises the saggingof the tubing over the break and may conveniently be a metallic sheet orfoil of, for example, hard-tempered aluminium or copper.

The bridging member preferably overlaps each of the edges of the breakby a distance at least equal to the width of the break.

The invention may also be employed in repairing roads where a crack hasalready appeared in a surface layer corresponding with an underlyingbreak in the concrete base layer. In such a case, a strip of the surfacelayer is removed to expose the break and a strip of the concrete baseeither side of the break, a bridging member is laid over the break andthe depression is then filled in with fresh tarry or bituminous materialup to the level of the road surface.

The invention also includes a method of constructing a road or likestructure comprising laying a concrete base layer followed by overlyingwith an adherent surface layer of a tarry or bituminous material whereinone or more breaks in the base layer are each covered prior to theapplication of the surface layer with a bridging member which overlapsthe edges of the break, the bridging member having at least on the uppersurface to be coated by the surface layer, a polymeric material which issubstantially resistant to tarry and bituminous products and has asoftening point above the temperature at which the surface layer isapplied to the concrete base layer.

Following is a description by way of example and with reference to theaccompanying drawing of a method of carrying the invention into effect.

Example Referring to the drawing, which is a diagrammatic longitudinalsection of part of a road, a concrete base layer 1, having an expansionjoint 2 one inch in width and plugged with a bituminous material, waslaid on a suitable foundation and after curing, a bridging member 3 waslaid over the joint. The bridging member 3 consisted of a length oftubing 4 in the flattened state having a width of ten inches, a wallthickness of two thousandths of an inch and manufactured frompolycaprolactam known as Nylon 6 which had a softening point at about221 C. A stiffeningmember 5 consisting of a strip of hard temperedaluminium foil 0.005 inch in thickness and seven inches in width wasenclosed within the'tubing 4. The bridging member 3 was placed centrallyover the joint 2 with its longitudinal axis parallel with the joint 2.

A surface layer 6 of asphalt, two inches in thickness, was then laid ata temperature of about 200 C. upon the concrete base layer 1 and overthe bridging member 3 and was consolidated by rolling. On cooling, thesurface layer 6 adhered to the base layer.

After a period of six weeks, it was observed that the surface layer 6was continuous over the area of the expansion joint.

In a control section of the road where the procedure was repeated exceptthat the bridging member 3 was omitted, it was observed that after aperiod of six weeks the surface layer 6 showed signs of cracking along aline corresponding with the expansion joint 2 beneath.

I claim:

1. A road structure comprising a concrete base layer having at least onebreak and overlaid with an adherent surface layer the adherent surfacelayer comprising a binding material selected from the group consistingof tar and bitumen, inlwhich road structure at least one break in theconcrete base layer is covered with a bridging member which overlaps theedges of the break, the bridging member having a synthetic polymericmaterial at least on the upper surface thereof in contact with thesurface layer the synthetic polymeric material being non-adherent andsubstantially resistant to tarry and bituminous products and having asoftening point above the temperature at which the surface layer isapplied to the concrete base layer and being selected from the groupconsisting of polycaprolactam, a condensation product of hexamethylenediamine and adipic acid, polytetrafluoroethylene,polychlorofluoroethylene and a polymer of 3,3 bis(chloromethyl)oxacyclobutane.

2. A road structure as claimed in claim 1 in which the bridging membercomprises a sheet of the synthetic polymeric material.

3. A road structure as claimed in claim 2 in which the bridging memberis supported by an underlying stiffening member.

4. A road structure as claimed in claim 3 in which the stiffening memberis a metallic sheet of metal selected from the group consisting ofhard-tempered aluminium and copper.

5. A road structure as claimed in claim 1 in which the bridging membercomprises a length of flattened tubing of the synthetic polymericmaterial.

6. A road structure as described in claim 5 in which a stiffening memberis inserted into the length of flattened tubing.

7. A road structure comprising a concrete base layer having at least onebreak and overlaid with an adherent surface layer the adherent surfacelayer comprising a binding material selected from the group consistingof tar and bitumen in which road structure at least one break in theconcrete base layer is covered with a bridging member which overlaps theedges of the break, the bridging member comprising a length of flattenedtubing of polycaprolactam in which is inserted a sheet of hard-temperedaluminium.

References Cited in the file of this patent UNITED STATES PATENTS854,135

OTHER REFERENCES Asphalts and Allied Substances, volumes 1 and 2; 5thedition, D. Van Nostrand Co. Inc., pages 77, 78, 101, 495, 836 and 1466.

7. A ROAD STRUCTURE COMPRISING A CONCRETE BASE LAYER HAVING AT LEAST ONEBREAK AND OVERLAID WITH AN ADHERENT SURFACE LAYER THE ADHERENT SURFACELAYER COMPRISING A BINDING MATERIAL SELECTED FROM THE GROUP CONSISTINGOF TAR AND BITUMEN IN WHICH ROAD STRUCTURE AT LEAST ONE BREAK IN THECONCRETE BASE LAYER IS COVERED WITH A BRIDGING MEMBER WHICH OVERLAPS THEEDGES OF THE BREAK, THE BRIDGING MEMBER COMPRISING A LENGTH OF FLATTENEDTUBING OF POLYCAPROLACTAM IN WHICH IS INSERTED A SHEET OF HARD-TEMPEREDALUMINUM.